diff --git a/genesis/engine/mesh.py b/genesis/engine/mesh.py
index 2afe406e1c..95f5d55fde 100644
--- a/genesis/engine/mesh.py
+++ b/genesis/engine/mesh.py
@@ -93,23 +93,15 @@ def decimate(self, decimate_face_num, decimate_aggressiveness, convexify):
         """
         if self._mesh.vertices.shape[0] > 3 and self._mesh.faces.shape[0] > decimate_face_num:
             self._mesh.process(validate=True)
-            # TODO: lossless option support is pending on fast_simplification package.
-            # NOTE: https://github.com/pyvista/fast-simplification/pull/71
-            if decimate_aggressiveness == 0:
-                gs.logger.debug("Lossless simplification is not supported yet. Not applying simplification.")
-                self._mesh = trimesh.Trimesh(
-                    vertices=self._mesh.vertices,
-                    faces=self._mesh.faces,
-                )
-            else:
-                self._mesh = trimesh.Trimesh(
-                    *fast_simplification.simplify(
-                        self._mesh.vertices,
-                        self._mesh.faces,
-                        target_count=decimate_face_num,
-                        agg=decimate_aggressiveness,
-                    )
+            self._mesh = trimesh.Trimesh(
+                *fast_simplification.simplify(
+                    self._mesh.vertices,
+                    self._mesh.faces,
+                    target_count=decimate_face_num,
+                    agg=decimate_aggressiveness,
+                    lossless=(decimate_aggressiveness == 0),
                 )
+            )
 
             # need to run convexify again after decimation, because sometimes decimating a convex-mesh can make it non-convex...
             if convexify:
diff --git a/genesis/utils/terrain.py b/genesis/utils/terrain.py
index f790c667e4..2268670ce7 100644
--- a/genesis/utils/terrain.py
+++ b/genesis/utils/terrain.py
@@ -386,14 +386,12 @@ def convert_heightfield_to_watertight_trimesh(
 
     # This is the mesh used for non-sdf purposes.
     # It's losslessly simplified from the full mesh, to save memory cost for storing verts and faces.
-    # TODO: lossless option support is pending on fast_simplification package.
-    # v_simp, f_simp = fast_simplification.simplify(
-    #     sdf_mesh.vertices,
-    #     sdf_mesh.faces,
-    #     target_count=0,
-    #     lossless=True,
-    # )
-    v_simp, f_simp = sdf_mesh.vertices, sdf_mesh.faces
+    v_simp, f_simp = fast_simplification.simplify(
+        sdf_mesh.vertices,
+        sdf_mesh.faces,
+        target_count=0,
+        lossless=True,
+    )
 
     if uvs is not None:
         idx_map = np.empty(len(v_simp), dtype=np.int64)
diff --git a/pyproject.toml b/pyproject.toml
index 81f75a4893..94efedcf2f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -60,7 +60,7 @@ dependencies = [
     # Native batch renderer specifically designed for Genesis
     "gs-madrona>=0.0.2; platform_system == 'Linux' and (platform_machine == 'x86_64' or platform_machine == 'AMD64')",
     # Used for mesh simplification
-    "fast_simplification",
+    "fast_simplification>=0.1.12",
 ]
 
 [project.optional-dependencies]